U.S. patent application number 11/649944 was filed with the patent office on 2007-07-19 for saw blade including teeth having a cutting portion with a wearing protection layer.
This patent application is currently assigned to WIKUS-Sagenfabrik Wilhelm H. Kullmann GmbH & Co. KG. Invention is credited to Jorg H. Kullmann, Werner Kwanka.
Application Number | 20070163392 11/649944 |
Document ID | / |
Family ID | 37890456 |
Filed Date | 2007-07-19 |
United States Patent
Application |
20070163392 |
Kind Code |
A1 |
Kullmann; Jorg H. ; et
al. |
July 19, 2007 |
Saw blade including teeth having a cutting portion with a wearing
protection layer
Abstract
A saw blade (15) includes a body (16) and a plurality of teeth
(1). The teeth (1) include a cutting portion (2) of a geometrically
defined shape and including a cutting edge (3). The cutting portion
(2) includes a wearing protection layer (7) which covers the
cutting edge (3). The cutting edge (3) has an edge radius (4)
between approximately 0.005 mm and 0.045 mm relating to a condition
of the cutting portion (2) without the wearing protection layer
(7). Preferably, the wearing protection layer (7) is made of a hard
material, especially TiN, TiCN, TiAlN, CrN or DLC.
Inventors: |
Kullmann; Jorg H.;
(Spangenberg, DE) ; Kwanka; Werner; (Vellmar,
DE) |
Correspondence
Address: |
THOMAS, KAYDEN, HORSTEMEYER & RISLEY, LLP
100 GALLERIA PARKWAY, NW, STE 1750
ATLANTA
GA
30339-5948
US
|
Assignee: |
WIKUS-Sagenfabrik Wilhelm H.
Kullmann GmbH & Co. KG
|
Family ID: |
37890456 |
Appl. No.: |
11/649944 |
Filed: |
January 5, 2007 |
Current U.S.
Class: |
76/112 ;
83/835 |
Current CPC
Class: |
B23D 61/12 20130101;
Y10T 83/9319 20150401; B23D 65/00 20130101; B23D 61/02 20130101;
B27B 33/02 20130101 |
Class at
Publication: |
76/112 ;
83/835 |
International
Class: |
B23D 57/00 20060101
B23D057/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 13, 2006 |
DE |
10 2006 001 816.8 |
Claims
1. A saw blade, comprising, a body; and a plurality of teeth, said
teeth including a cutting portion of a geometrically defined shape,
said cutting portion including a cutting edge, said cutting portion
including a wearing protection layer, said wearing protection layer
being designed and arranged to cover said cutting edge, said
cutting edge having an edge radius between approximately 0.005 mm
and 0.045 mm relating to a condition of said cutting portion
without said wearing protection layer.
2. The saw blade of claim 1, wherein said edge radius is
approximately between 0.010 mm and 0.025 mm.
3. The saw blade of claim 1, wherein said body and said teeth are
made of hard metal and said wearing protection layer includes hard
material.
4. The saw blade of claim 2, wherein said body and said teeth are
made of hard metal and said wearing protection layer includes hard
material.
5. The saw blade of claim 1, wherein said teeth include carbide
inserts and said wearing protection layer is made of hard
material.
6. The saw blade of claim 2, wherein said teeth include carbide
inserts and said wearing protection layer is made of hard
material.
7. The saw blade of claim 1, wherein said wearing protection layer
has a thickness of approximately between 0.002 mm and 0.008 mm.
8. The saw blade of claim 2, wherein said wearing protection layer
has a thickness of approximately between 0.002 mm and 0.008 mm.
9. The saw blade of claim 3, wherein said wearing protection layer
has a thickness of approximately between 0.002 mm and 0.008 mm.
10. The saw blade of claim 4, wherein said wearing protection layer
has a thickness of approximately between 0.002 mm and 0.008 mm.
11. The saw blade of claim 1, wherein said wearing protection layer
includes an intermediate layer and a surface layer, said
intermediate layer being designed and arranged for providing a fix
connection with said cutting portion, said surface layer being
designed and arranged for providing hardness and wearing
resistance.
12. The saw blade of claim 2, wherein said wearing protection layer
includes an intermediate layer and a surface layer, said
intermediate layer being designed and arranged for providing a fix
connection with said cutting portion, said surface layer being
designed and arranged for providing hardness and wearing
resistance.
13. The saw blade of claim 11, wherein said intermediate layer
includes a material selected from the group consisting of TiN,
TiCN, TiAlN and CrN and said surface layer includes DLC.
14. The saw blade of claim 12, wherein said intermediate layer
includes a material selected from the group consisting of TiN,
TiCN, TiAlN and CrN and said surface layer includes DLC.
15. The saw blade of claim 13, wherein said intermediate layer has
a thickness of approximately between 0.002 mm and 0.004 mm.
16. The saw blade of claim 13, wherein said surface layer has a
thickness of approximately between 0.002 mm and 0.004 mm.
17. The saw blade of claim 13, wherein said intermediate layer has
a thickness of approximately between 0.002 mm and 0.004 mm and said
surface layer has a thickness of approximately between 0.002 mm and
0.004 mm.
18. The saw blade of claim 1, wherein said edge radius is
determined in response to a point of intersection of a course of
the bonding properties of said wearing protection layer on said
cutting portion and a course of the cutting force.
19. The saw blade of claim 2, wherein said edge radius is
determined in response to a point of intersection of a course of
the bonding properties of said wearing protection layer on said
cutting portion and a course of the cutting force.
20. A method of producing a saw blade including a body and a
plurality of teeth, said method comprising the steps of: grinding a
tooth for producing a cutting portion of a geometrically defined
shape and including a cutting edge; finishing said cutting portion
in a way that said cutting edge has an edge radius between
approximately 0.005 mm and 0.045 mm; and applying a wearing
protection layer on said cutting portion in a way that said wearing
protection layer covers said cutting edge.
21. The method of claim 20, wherein said edge radius is
approximately between 0.010 mm and 0.025 mm.
22. The method of claim 20, wherein said step of finishing is
realized by a method selected from the group consisting of
brushing, abrasive-blasting and trimming.
23. The method of claim 21, wherein said step of finishing is
realized by a method selected from the group consisting of
brushing, abrasive-blasting and trimming.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to co-pending German Patent
Application No. DE 10 2006 001 816.8 entitled "Sageblatt mit einem
Grundkorper und Zahnen mit einer Schneide mit einer
Verschlei.beta.schutzschicht", filed Jan. 13, 2006.
FIELD OF THE INVENTION
[0002] The present invention generally relates to a saw blade
including a body and a plurality of teeth each including a cutting
portion of a geometrically defined shape and including a cutting
edge. A wearing protection layer covers the cutting edge of the
cutting portion.
[0003] Especially, the saw blade is a saw band or a circular saw
blade. Especially, at least the teeth are at least partly made of
hard metal.
[0004] It is to be understood that the present specification and
claims relate to a cutting portion of a geometrically defined
shape. This is a technical term as defined in German standard DIN
8580 which defines cutting-off methods removing chips and using a
cutting portion of a geometrically defined shape as turning on a
lathe, drilling, milling, planing, broaching, sawing and filing. In
contrast thereto, cutting-off methods removing chips using a
cutting portion of a geometrically undefined shape are defined as
grinding, honing and lapping, for example.
BACKGROUND OF THE INVENTION
[0005] A saw band including a body and a plurality of teeth each
including a cutting portion of a geometrically defined shape and
including a cutting edge are known from the website of Tungsten
Tool & Saw Co., Toronto/Canada at
www.tungstentool.com/amada_aurora.html. A wearing protection layer
covers the cutting edge of the cutting portion. The wearing
protection layer is made of titanium nitrite (TiN). There is the
problem with this known saw band that the wearing protection layer
gets detached from the teeth during operation of the saw band
already after a comparatively short period of time and that the
properties reducing wear get lost.
[0006] A saw band including a body and a plurality of teeth each
including a cutting portion of a geometrically defined shape and
including a cutting edge are known from the website of American Saw
& Mfg. Company, East Longmeadow, USA operating under the
trademark "LENOX" at www.lenoxsaw.com/armor_blk.html. The cutting
edge of the cutting portion is covered by a wearing protection
layer. The wearing protection layer is made of aluminium titanium
nitrite (AlTiN). There is the problem with this known saw band that
the wearing protection layer gets detached from the teeth during
operation of the saw band already after a comparatively short
period of time and that the properties reducing wear get lost.
[0007] Another saw band including a body and a plurality of teeth
each including a cutting portion of a geometrically defined shape
and including a cutting edge is known from the website of American
Saw & Mfg. Company, East Longmeadow, USA operating under the
trademark "LENOX" at www.lenoxsaw.com/armor_gold.html. The cutting
edge of the cutting portion is covered by a wearing protection
layer. The wearing protection layer is made of titanium nitrite
(TiN). There also is the problem with this known saw band that the
wearing protection layer gets detached from the teeth during
operation of the saw band already after a comparatively short
period of time and that the properties reducing wear get lost.
[0008] A saw blade including a body and a plurality of teeth each
including a cutting portion of a geometrically defined shape and
including a cutting edge is known from German Patent No. DE 43 00
622 C2 corresponding to U.S. Pat. No. 5,477,763 and U.S. Pat. No.
5,425,296. The teeth may include carbide inserts which attain their
final shape by a grinding operation, especially in the region of
the cutting edge. Additional measures for reducing wear are not
disclosed.
[0009] Saw bands including a body including a galvanic coating of
diamond particles in the region of the continuous or broken edge
are known from the leaflet "Precision Band Saw Blades", edition
2005, pages 44-46 of WIKUS-Sagenfabrik Wilhelm H. Kullmann GmbH
& Co. KG. Thus, this is a saw band including a multitude of
cutting portions of geometrically undefined shape being formed by
the diamond particles. There are no teeth in the sense of elements
protruding from the body at a chip angle. Such saw bands including
cutting portions of geometrically undefined shape rather operate in
a grinding way. The thickness of the galvanic coating is
approximately between 0.3 mm to 0.4 mm. The diamond particles are
fixedly located in a nickel layer. However, bonding of the galvanic
layer on the material of the body is insufficient such that there
are cracking effects in the region of the cutting portions when
using such saw bands.
[0010] Furthermore, tools removing chips and having a cutting
portion of geometrically defined shape, namely drills, are known
from the website of Plasma+Rubber-coatings AG, Schaan Liechtenstein
at www.rhenotherm.de/Dlcdlc.html. A wearing protection layer is
located in the region of the body. The wearing protection layer is
a DLC layer (DLC=diamond-like carbon) which is hard and brittle.
The DLC layer has a small coefficient of friction such that when
using it the chip flow is only disturbed to a comparatively small
extent and such that there only is a moderate increase of
temperature. The DLC layer is deposited by a CVD process
(CVD=chemical vapour deposition).
[0011] As it is generally known in the prior art, the above
described CVD process is mostly conducted at reduced pressure and
at high temperatures. It finds its limits in the temperature
stability of the material of the body such that the use of the CVD
process is limited to tools removing chips such as drills for which
the geometric dimensions of a cutting portion have a certain
relation with respect to the chip thickness. Typically, such drills
have cutting edges with an edge radius of between 0.060 mm and
0.200 mm. The associated chip thicknesses are in a range of
approximately 0.200 mm to 0.800 mm. These conditions substantially
differ from the geometric conditions as they prevail when sawing
with saw blades.
[0012] Furthermore, saw blades including a body and a plurality of
teeth each including a cutting portion of geometrically defined
shape and including a cutting portion are generally known in the
prior art. The cutting portion is made of hard metal, and it is
finished by grinding the tooth face and the tooth back. The average
"edge radius" is between 0.005 mm and 0.010 mm in the ground state
of the tooth face and the tooth back. However, this "edge radius"
rather is an accidental ragged design of the cutting portion. The
cutting edge itself is not machined. When considering the size and
the accidental irregular shape, it is rather not appropriate to
designate this shape as an edge radius. The corresponding chip
thickness is in a range of approximately 0.003 mm to 0.020 mm.
There are no special measures for reducing wear.
SUMMARY OF THE INVENTION
[0013] The present invention relates to a saw blade including a
body and a plurality of teeth. The teeth include a cutting portion
of a geometrically defined shape. The cutting portion includes a
cutting edge. The cutting portion includes a wearing protection
layer. The wearing protection layer is designed and arranged to
cover the cutting edge. The cutting edge has an edge radius between
approximately 0.005 mm and 0.045 mm relating to a condition of the
cutting portion without the wearing protection layer.
[0014] The present invention also relates to a method of producing
a saw blade including a body and a plurality of teeth. The method
includes the steps of grinding a tooth for producing a cutting
portion of a geometrically defined shape and including a cutting
edge; finishing the cutting portion in a way that the cutting edge
has an edge radius between approximately 0.005 mm and 0.045 mm; and
applying a wearing protection layer on the cutting portion in a way
that the wearing protection layer covers the cutting edge.
[0015] The novel saw blade includes teeth having a cutting portion
which is designed such that protection against wear lasts longer
and is improved compared to the prior art.
[0016] The present invention is based on the surprising perception
that for improving the wear properties of a saw blade, this saw
blade initially needs to be subjected to certain "wear" in a
conscious and defined way. Afterwards, the wearing protection layer
can be deposited on the saw blade, and it adheres substantially
better and longer on the cutting portion than it is the case when
depositing it on a non-machined, irregular and sharp cutting edge
as it is known in the prior art. More particularly, the defined
wear is realized by applying an edge radius at the cutting edge of
the cutting portion of the saw blade which is between approximately
0.005 mm and 0.045 mm. These values relate to a condition of the
saw blade without the wearing protection layer. It is to be
understood that after depositing the wearing protection layer, the
wearing protection layer with its outer surface forms the effective
cutting portion and the cutting edge. Consequently, depending on
the thickness of the wearing protection layer there is a different
(meaning greater) effective edge radius when measuring it after the
deposition of the wearing protection layer.
[0017] First of all, it needs to be considered that when sawing
material--compared to other cutting-off methods removing chips and
including a cutting portion of geometrically defined shape, for
example drilling or milling--it is desired to remove comparatively
thin chips. The cutting forces to be applied during sawing are
mostly proportional to the chip thickness. In other words, thicker
chips require higher cutting forces than thinner chips. It is a
perception of the inventors that positive process results are
realized when producing an effective chip thickness during sawing
which is in a range of approximately 0.015 mm to 0.030 mm. The
effective chip thickness is the actual feed per tooth. The
effective chip thickness is to be differentiated from the
theoretical feed per tooth. The actual feed per tooth results from
the distribution of the cutting channel in cutting segments which
are associated with certain teeth. Until now, it was the perception
of a person with skill in the art that such thin chips can only be
produced with saw blades having very sharp cutting edges. This
means that the "edge radius" of the cutting portion at each tooth
should be designed to be very small. In case the cutting edges made
of hard metal are produced by grinding the tooth face and the tooth
back, such a saw blade having comparatively sharp teeth may be
produced without substantial problems. The teeth have a very small
edge radius which is approximately in a range of 0.005 mm. However,
this rather is an accidental ragged design of the cutting portion.
The cutting edge itself is not machined. It is rather inappropriate
to designate such a design as having an edge radius when
considering its size and its accidental irregular shape.
[0018] The present invention is also based on the perception that
it makes sense to improve the properties of saw blades by
depositing at least one wearing protection layer on the cutting
portions of the teeth at least in the region of the cutting edge.
The wearing protection layer or wearing protection coating may
cover the entire cutting portion, the entire tooth, a part of the
body or even the entire saw blade, for example. However, a design
is preferred in which the wearing protection layer covers the
entire cutting portion and a part of the body. In contrast to the
prior art, it is desired that the novel wearing protection layer
sufficiently adheres to the material of the body and of the teeth,
respectively, as it corresponds to the predetermined lifetime of
the saw blades. The wearing protection layer is chosen such that it
provides improved properties during sawing. For example, it is
desired that such a wearing protection layer has an increased
hardness and consequently an improved resistance against abrasion
to be capable of achieving a longer service life of the novel saw
blade. It is also advantageous if the coefficient of friction of
such a wearing protection layer is comparatively small to achieve
the results of a good flow of the chips during sawing and low
heating effects of the saw blade itself.
[0019] Bonding of such wearing protection layers in the region of
sharp cutting edges of the cutting portion of a tooth of saw blades
of the prior art shows problems, as it has been perceived by the
present invention. This especially applies when using small edge
radiuses, for example such ones in a range of between 0.005 mm and
0.010 mm. In this case, the applied wearing protection layers of
the prior art are under tension which may lead to the wearing
protection layers not permanently adhering, but in the worst case
getting detached from the surface very quickly due to release of
the internal stress. Forces acting during sawing may also cause or
at least promote such a detachment process of wearing protection
layers in the prior art such that there are no sufficient usable
times of such known saw blades.
[0020] The present invention consciously gives up the goal of
attaining cutting edges having a design as sharp as possible. With
the present invention, the geometrical conditions in the region of
the cutting edge are limited to value ranges which make it possible
to attain an optimum between the contrary demands of a sharp saw
blade, on the one hand, and sufficient bonding of the wearing
protection layer, on the other hand. This optimum is coordinated
with a chip thickness in a range between 0.015 mm and 0.030 mm. An
edge radius is chosen which is slightly greater than the edge
radius which could be produced by grinding. The edge radius being
increased insofar leads to the saw blade being less sharp. The edge
radius is determined in a range between 0.004 mm and 0.05 mm.
Especially good working results are achieved when the edge radius
is between 0.010 mm and 0.025 mm. It is to be understood that the
edge radius as seen under a microscope is no exact radius since
such an exact radius cannot be produced in reality. However, the
average radius is in the above mentioned value range. The term
radius as used in this application is also to be understood as
relating to a different bent design which also leads towards the
goal of leaving the sharp shape of the non-machined cutting edge.
In this way, one attains sufficient bonding properties of the
wearing protection layer and a respective service life of the saw
blade. At the same time, compared to saw blades of the prior art,
the cutting force at a certain comparison point in time after a
certain action time of the novel saw blade and of a saw blade of
the prior art is reduced by the novel saw blade since the above
explained portions of the edge radiuses of the novel saw blade are
then still smaller than the ones of the saw blades of the prior art
(which are already worn-out to a greater extent at this comparative
point in time).
[0021] The cutting portion of the saw blade preferably is made of
hard metal, meaning especially steel being alloyed with tungsten
and/or cobalt. Tungsten is the actual hard material and cobalt--as
well as other possible alloys--is the binder. However, it is also
possible to use super-speed steel, for example. The wearing
protection layer may be made of hard material. Especially, hard
material is to be understood as including TiN, TiCN, TiAlN, CrN and
DLC. The wearing protection layer may be designed to include one or
more layers. When using a single layer design, the wearing
protection layer is especially made of TiN, TiCN, TiAlN or CrN. It
is also possible that a plurality of different layers--for example
two, three or even four layers--form the wearing protection layer.
When using such a multi-layer design, the at least one intermediate
layer is especially made of TiN, TiCN, TiAlN or CrN and the surface
layer being located on the intermediate layer is especially made of
DLC. Preferably, the wearing protection layer is deposited by a PVD
process (PVD=physical vapor deposition). When using a multi-layer
design, this applies to the surface layer as well as to the at
least one intermediate layer.
[0022] Usually, the cutting portions of the teeth of the novel saw
blade will be produced by grinding. Grinding is followed by a
finishing process which desires to reduce the ragged design of the
cutting edge and to increase the edge radius, respectively, and to
round the cutting edge before applying the wearing protection
layer. This finishing process desiring to reduce the ragged design
and to round the cutting edge may be especially realized by
brushing, abrasive-blasting or trimming, meaning by measures which
apply a rounding effect and a leveling effect to the cutting edge.
However, the finishing process is to be chosen such that one does
not attain dull saw blades, meaning no saw blades as they prevail
due to wear at the end of their service life. It is also desired to
prevent properties of saw blades with which the chips to be removed
are comparatively thick, meaning in a range of approximately 0.060
mm.
[0023] The material of the body of the saw blade is preferably made
of hard metal. The saw blade especially is a saw band or a circular
saw blade. The body of a saw band is the back of the band from
which the teeth protrude. In this case, the teeth are also made of
hard metal, they are initially produced by milling and they are
later finished by grinding. However, the teeth may also only
include inserts made of hard metal. In this case, the teeth (not
including the inserts) and the body are made of a softer material,
for example steel. Furthermore, the inserts of hard metal may
include PKD (PKD=polycrystalline diamond). In the following, the
teeth are finished. In this way, the geometrical shape of the
cutting portion is determined before depositing the wearing
protection layer.
[0024] It is especially preferred to deposit a multi-layer,
especially a two-layer wearing protection layer on the material of
the body and of the teeth in the region of the cutting portions of
the teeth, respectively. Preferably, at first an intermediate layer
made of a material selected from the group consisting of TiN, TiCN,
TiAlN and CrN is applied. The thickness of the intermediate layer
preferably is in a range of approximately between 0.002 mm to 0.004
mm. The intermediate layer has the goal of improving bonding of a
surface layer and also to act as a barrier layer between the
surface layer and the material of the body and of the tooth,
respectively. This especially applies when the preferred DLC layer
is used as the surface layer. The surface layer also preferably has
a thickness of approximately between 0.002 mm to 0.004 mm. In this
way, the finished (complete) tooth has a layer thickness of the
complete (two-layer) wearing protection layer of between
approximately 0.004 mm to 0.008 mm and effective cutting edge
radiuses in a range of approximately between 0.016 mm to 0.031 mm,
meaning exactly such ones in the region of the predetermined chip
thickness.
[0025] Other features and advantages of the present invention will
become apparent to one with skill in the art upon examination of
the following drawings and the detailed description. It is intended
that all such additional features and advantages be included herein
within the scope of the present invention, as defined by the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The invention can be better understood with reference to the
following drawings. The components in the drawings are not
necessarily to scale, emphasis instead being placed upon clearly
illustrating the principles of the present invention. In the
drawings, like reference numerals designate corresponding parts
throughout the several views.
[0027] FIG. 1 is a general plan view of a section of a first
exemplary embodiment of the novel saw blade being designed as a saw
band.
[0028] FIG. 2 is a general plan view of a section of a second
exemplary embodiment of the novel saw blade being designed as a saw
band including carbide inserts.
[0029] FIG. 3 is a view of a third exemplary embodiment of the
novel saw blade being designed as a circular saw blade.
[0030] FIG. 4 is a strongly enlarged view of the tip of a tooth of
the novel saw blade during sawing.
[0031] FIG. 5 is a further enlarged view of the tip of a partly
worn-out tooth during sawing.
[0032] FIG. 6 is a diagram illustrating the cutting force and the
bonding properties of a wearing protection layer on the Y-axis and
the edge radius on the X-axis.
[0033] FIG. 7 shows a microscopic recording of the tip of a tooth
of the novel saw blade, the tooth including a wearing protection
coating.
DETAILED DESCRIPTION
[0034] Referring now in greater detail to the drawings, FIG. 1
illustrates a general plan view of a part of a first exemplary
embodiment of a novel saw blade 15 being designed as a saw band 17.
The saw blade 15 includes a body 16 and a plurality of teeth 1.
FIG. 1 only illustrates a part of the saw blade 15 such that only a
part of its body 16 and only a part of its teeth 1 are visible. It
is to be understood that the body 16 includes further teeth 1 along
its extension.
[0035] FIG. 2 is a general plan view illustrating a part of a
second exemplary embodiment of the novel saw band 15 being designed
as a saw band 18 including carbide inserts 19. The carbide inserts
19 may however also have a different shape.
[0036] FIG. 3 illustrates a third exemplary embodiment of the novel
saw blade 15 being designed as a circular saw blade 20. The
circular saw blade 20 may however also include carbide inserts.
[0037] FIG. 4 is an enlarged illustration of the tip of a tooth 1
during sawing. The exemplary tooth 1 is a tooth of one of the
embodiments of the saw blades 15 being illustrated in FIGS. 1-3.
The tooth 1 includes a cutting portion 2. The tooth 1 is at least
partly made of hard metal extending over the entire region of its
cutting portion 2. The cutting portion 2 ends in a cutting edge 3
having an associated edge radius 4. The edge radius 4 is
approximately between 0.005 mm and 0.045 mm, especially
approximately between 0.010 mm and 0.025 mm. The edge radius 4 has
been produced by grinding, and it is limited to the defined region
by finishing. The tooth back 22 and the tooth face 23 are located
next to the cutting edge 3.
[0038] In this way, the cutting portion 2 having a geometrically
defined cutting shape is formed in a preliminary way. The
preliminary cutting portion 2 is covered by an intermediate layer 5
and a surface layer 6 being located thereon, the two layers 5 and 6
forming a wearing protection layer 7. In the described case, the
wearing protection layer 7 includes two layers. However, it is to
be understood that the wearing protection layer 7 may also be made
of one single layer or of more than two layers. In the present
case, the intermediate layer 5 includes titanium nitrite (TiN), and
the surface layer 6 includes DLC (diamond-like carbon). The layers
5, 6 are deposited one after the other by a PVD process (physical
vapor deposition process). In this way, the outer surface of the
wearing protection layer 7 forms the effective cutting edge during
actual cutting and sawing, respectively.
[0039] Such a novel saw blade 15 with its multitude of such teeth 1
penetrates into the material of a work piece 8 from the side of its
surface 9, and it removes a chip 10 and a series of chips 10,
respectively, during sawing. In this way, a chip thickness 11 is
attained. It is desired to attain a chip thickness 11 having a size
in the range between approximately 0.015 mm and 0.030 mm depending
on the above described size of the cutting portion 2 and of the
cutting edge 3, respectively. It is to be seen that the edge radius
4 has a value in a range which approximately corresponds to the
range of the chip thickness 11. The range may be identical or
slightly less than the range of the chip thickness 11. In this way,
one attains a saw blade 15 having sufficiently sharp teeth 1
removing comparatively thin chips 11 from the work piece 8 while
the required cutting force is kept low in an advantageous way and
the properties of the surface layer 6 result in easy chip flow and
low heating of the teeth 1. However, the wearing protection layer 7
securely adheres to the teeth 1.
[0040] FIG. 5 illustrates an even more enlarged view of the tip of
the tooth 1 according to FIG. 1 during sawing. However, FIG. 5
illustrates a condition in which the saw blade 15 already has gone
through a certain action time. Correspondingly, it is to be seen
that the wearing protection layer 7 has already been partly
removed. The cutting portion 2 also does not have its initial
shape. However, FIG. 5 also illustrates that parts of the wearing
protection layer 7 are still there and that they still contact the
chips. Consequently, the wearing protection layer 7 still fulfills
a part of its wearing reducing effect such that even in this
condition it still increases the working life of the saw blade
15.
[0041] FIG. 6 is a diagram schematically emphasizing the optimal
coordination of the geometric shape of the teeth 1 in the region of
the cutting portion 2 and of the cutting edge 3, respectively, with
respect to the bonding properties of the wearing protection layer
7. The diagram only serves to emphasize the tendency. The abscissa
(X-Axis) shows the edge radius 4. The ordinate (Y-Axis) shows the
cutting force, on the one hand, and the bonding properties of the
wearing protection layer 7, on the other hand.
[0042] As a result, there is an ascending continuous curve 12
illustrating the cutting force being required for cutting a work
piece 8. The cutting force increases when the edge radius 4 is
increased. This relation has been experienced before in the sense
of a worn-out, dull saw blade 15 requiring a greater cutting force
than a new, sharp saw blade 15. In other words, the cutting force
is advantageously small when designing the cutting edge 3 to be
very sharp. The dot-dash line 13 however shows that the bonding
properties of the wearing protection layer 7 are reduced when the
edge radius 4 is reduced. This tends to lead to the effect of the
wearing protection layer 7 not being capable of fulfilling its
function in the desired way. The point of intersection 14 results
from these two opposite tendencies and from the respective course
of the respective course of the curves 12, 13, respectively.
Optimal conditions prevail in the point of intersection 14.
According to the present invention, the point of intersection 14 is
located at an edge radius 4 of between approximately 0.005 mm and
0.045 mm, especially between approximately 0.010 mm and 0.025
mm.
[0043] Finally, FIG. 7 shows a microscopic recording of a tip of a
tooth 1 of the novel saw blade 15, the tooth 1 including a wearing
protection layer 7. The edge radius 4 is approximately 0.016 mm. It
is to be seen that the edge radius 4 as seen microscopically is no
exact radius since such an exact radius cannot be produced in
reality. However, the average edge radius 4 has the above mentioned
value.
[0044] Many variations and modifications may be made to the
preferred embodiments of the invention without departing
substantially from the spirit and principles of the invention. All
such modifications and variations are intended to be included
herein within the scope of the present invention, as defined by the
following claims.
* * * * *
References